Ultra-small electronic devices are usually packed by placing them into respective pockets of a carrier tape. This packing process often requires high precision as there tends to be little clearance between the walls of each pocket and the device to be placed into the pocket. This is especially so for certain types of devices such as devices with dimensions of 0.6 mm by 0.3 mm, or 0.4 mm by 0.2 mm (typically referred to as 0603 or 0402 respectively). In fact, the clearance may sometimes be smaller than the positional tolerance of the carrier tape. The clearance is even smaller if the carrier tape is in the form of a paper tape having pockets with straight vertical walls.
To facilitate packing of ultra-small electronic devices, prior art methods have been developed to improve the alignment of each electronic device with the respective pocket before placing the device into the pocket.
One example of such a prior art method is described in TW201607842. In TW201607842, a carrier tape having multiple pockets is conveyed by two sprockets, and a main body supports the sprockets together with the carrier tape. An imaging unit is used to capture an image of the pocket and the captured image is analysed to determine the offset in the position and orientation of the pocket relative to a reference position and orientation. A correction unit then moves the main body along an X-Y plane and rotates the main body about a Z axis. This in turn moves the pocket of the carrier tape to compensate for the determined offset. The alignment between the pocket and the electronic device to be placed into the pocket is hence improved.
FIG. 1 and FIG. 2 show a prior art apparatus 100 for packing ultra-small electronic devices 102. In FIG. 1 and FIG. 2, the carrier tape 104 is supported by an index wheel, which is in turn supported by a main body (the main body and index wheel are not shown in FIG. 1 and FIG. 2). The apparatus 100 comprises a turret 106 having a plurality of pick heads 108 for holding respective electronic devices 102. Each pick head 108 is moved sequentially through a series of stations, including a precising station and an imaging station. Referring to FIG. 1, at the precising station, a precising mechanism in the form of a precisor re-orientator 110 is used to adjust an orientation of the electronic device 102 to correct angular displacement errors, and at the imaging station, a vision camera in the form of an up-look camera 112 is used to capture an image of each pick head 108 (hence, an image of the electronic device 102 held by the pick head 108). The apparatus 100 further comprises a pocket alignment inspection camera in the form of a down-look camera 114 attached to the turret 106. Referring to FIG. 2, the up-look camera 112 captures an image of the electronic device 102 held by the pick head 108. The down-look camera 114 is positioned over the carrier tape 104, and captures an image of the carrier tape 104 (hence, capturing an image of the pocket 116 which the next electronic device 102 is to be placed into). Using the captured images, an expected offset in the relative position of the electronic device 102 and the pocket 116 which the electronic device 102 is to be placed into is calculated. An X-Y table 118 then moves the main body in the X-Y plane to adjust a position of the carrier tape 104 based on the calculated offset. This improves the alignment between the electronic device 102 and the pocket 116 the device 102 is to be placed into.
Although the prior art methods described above are able to improve the alignment between the electronic devices and the respective pockets, the time taken to adjust the relative position between each device and the respective pocket is relatively long. This is because the correcting mechanism (such as the correction unit in TW201607842 and the X-Y table 118 of the apparatus 100) usually carries a heavy load and therefore, tends to move at a low speed. Furthermore, the main body moved by the correcting mechanism is also heavy. As a result, the improvement in alignment between the electronic devices and the respective pockets is often at the expense of reduced system throughput.